Hospitals and residences for handicapped individuals and the elderly are typically equipped with transportation systems for lifting and transferring patients between locations. A conventional patient transport system includes a truck that travels along ceiling-mounted rails, for example, running between a bed and a tub or toilet, and a load carrier suspended from the truck. The load carrier can be moved manually or equipped with drive motors for moving the truck along the rails and for powering a lifting and lowering mechanism. One or more batteries are included in the load carrier for supplying power to the drive motors. The batteries are electrically connectable to a charging unit via means provided on the truck and/or rails.
FIG. 1 shows one known conventional system for charging the batteries of the patient transport system described above. A charging, or parking, station 1 is disposed in a rail and positioned at a terminal end thereof. A local or remote charging unit (not shown) is connected to the charging station 1. The engaging end 3 of the charging station has elements 5 for effecting electrical engagement with complementary elements 6 provided on one end of the a movable truck 11. As shown in FIG. 1, the mating elements 5, 6 typically include spring-loaded prongs 7 extending from the charging station 1 and mating contacts 9 provided on the movable truck 11. When engaged with the contacts 9, the prongs 7 deliver current from the charging unit to the batteries (not shown) via electrical conductors 13 extending between the contacts 9 and the batteries. The truck 11 and the charging station 1 are provided with securing means 15, such as an extension 17 engageable in a receiving channel 19 with spring-loaded balls 18 for releasably holding the truck 11 in a charging position.
The system shown in FIG. 1 has certain disadvantages and limitations. First, the charging station is disposed in the path of travel of the truck, and therefore can only be positioned at an end of the rail. Second, the number of possible charging stations is limited, as only one end of the truck is typically equipped with the necessary mating elements and no intermediate stations are possible. Third, the inclusion of mating means on one end of the truck increases the length of the truck, necessitating a larger turning radius for the truck and thereby imposing design limitations on the rail system. Finally, the mating mechanical and electrical elements of the system shown in FIG. 1 occasionally become disengaged so that battery charging is interrupted.
A typical patient transport device having a continuous charging system is disclosed in U.S. Pat. No. 5,138,953. According to the apparatus disclosed in that patent, a transportation device includes bus bars in the form of copper strips on top of insulating layers fastened to the insides of vertically-extending side walls of each rail. Carbon brushes extending from the sides of a movable truck bear against the copper strips and tap the DC voltage at the copper strips. Current is continuously transferred via conductors extending between the brushes and the battery and drive motors. While the device disclosed in U.S. Pat. No. 5,138,953 provides for charging of the battery at any position along the rail, it is not cost effective and is subject to failure, particularly when used in combination with jointed rail systems, as the brushes can become damaged when traversing joints in the rails.
It would be desirable therefore to provide a method of and an apparatus for charging batteries of patient transport systems that are economical and dependable, provide for the multiple, conveniently located charging stations, are suitable for use on jointed and continuous rail systems, and do not place significant restrictions on rail design.